The goal of this project is to study the role of carbohydrate determinants in the antigenic makeup of human tumor cells and to develop mouse monoclonal antibodies to such structures for possible use in the diagnosis of cancer. Many of the mouse monoclonal antibodies raised to human tumors, particularly to epithelial tumors, have been shown to be directed to carbohydrate determinants. Prominent among these are antibodies to blood group structures: A, B, H, Lea, Leb, X, and Y. The possibility that the expression of these antigens is of diagnostic value in individuals of the appropriate genetic makeup is being investigated. Other antibodies recognize novel carbohydrate antigens whose structure will be investigated. Another approach to this problem that is being pursued is to develop monoclonal antibodies to lectin-resistant variants of human tumor cell lines on the assumption that such variants will have novel carbohydrate structures that may be found in certain tumor types. The availability of pairs of "wild-type" and "variant" cell lines will provide an ideal series for the detection of antibodies of the desired properties. Concanavalin A, wheat germ agglutinin, and ricin-resistant lines have been produced as the initial step in this study. (2)